How do File Descriptors affect ZXTM?

Configuring File Descriptor limits.

Before deploying a live system, you should perform load testing to establish whether you are likely to experience any bottlenecks with your projected levels of traffic.

Running out of operating system resources such as file descriptors is a very common cause of system instablity and can display a large variety of symptoms which may be difficult to attribute to this exhaustion of OS resource.

You may find warning messages in the ZXTM Alert Log containing:

WARN:Running out of free file descriptors, see documentation for information on how to increase limit

Assuming that this shortage is a process limitation rather than a global limitation (for more details see your OS instructions), then there are two ways to resolve the issue:

• Raise the OS limit on the number of file descriptors available to a particular process,
• Run more zeus.zxtm child processes.

The first method is preferred, since using more zeus.zxtm child processes means that your system may not perform as well.

If your operating system does not easily allow you to increase the file descriptor limit, it may be easier to run more zeus.zxtm child processes. Details of how to do this can be found on the settings page, where 'num_children' is the tunable in question.

Please note that the advice above is provided only as a general introduction to issues related to file descriptors and is not a substitute for Operating System documentation. For detailed performance tuning advice unique to your system and projected traffic levels our Professional Services Group can offer further information. Hardware vendors may like to consider our Performance Engineering Partnership program.

Owen Garrett [Zeus Dev Team] 01 July 2005